This is a very interesting thread...Being on both ends...we have our own Semi that we haul cattle and feed...plus a 1ton pickup that we haul everything from horsetrailers to flatbeds full of stuff...so needless to say I've ridden in both situations.  Out here in the wideopen spaces of Nebraska, we don't run into to many "hairy" situations, but there have been times that folks in the RV's or pulling large camper trailers, have caused more concern for us than anything.  I agree that they should have some kind of instruction and lisence to be able to drive them.  I don't want to single out the "older crowd" but they seem to be the ones that does the most driving, and the most not looking where they're going or the situation they are in...Pulling horse trailers in this country is second nature, but Semi trucks always have the respect and the room they need, no matter if they are in the wrong..or in the right!  Glad that you're alright shoer...bet it added a grey hair or two!  That's just my 3 cents worth..